The CENSUS system is a set of computer programs which enables the storage and retrieval of a data base of information on cancer patients treated at the Baltimore Cancer Research Program. The computer programs and the data base are accessed from remote terminals connected to a commercial time-sharing computer facility. Structured data input programs facilitate the addition of new information to the data base. A flexible retrieval program produces patient listing sorted by patient name, cancer diagnosis, attending physician, and/or status. A data processor updates the data base daily and then generates a CENSUS report which lists all patients currently on the Clinical Oncology inpatient service and Clinical Oncology clinical visits made that day. The system has been in operation since August of 1971, and the data base currently contains records of over 2400 cancer patients. This system has been converted to run on the PROMIS system in conjunction with an Interagency Agreement with the National Center for Health Services Research (Y01 CM 80109). The CENSUS system will, in the future, operate as a su bset of the PROMIS system.